The mechanism for the regulation of triglyceride biosynthesis in intestinal mucosa has been further studied. The original hypothesis concerning the inhibition of glycerol-3-phosphate acylation by monoglycerides has been further extended by the demonstration that the sn-1,2, and 3 stereochemical ether analogs of mono-olein inhibit the acylation of glycerol-3-phosphate. The monoglyceride and glycero-3-phosphate pathways have also been examined in microsomes obtained from the intestinal tip and crypt cells. Both activities are increased in the microsomes obtained from tip cells. We have suggested that the mechanism of induction of the monoglyceride pathway is a substrate-induction. This is supported by the observations that the monoglyceride pathway in the rat and rabbit is induced when the gestational period is 80% complete and the fetus is swallowing amniotic fluid containing neutral lipids. In studies on fetal lung development it has been shown that the activity of phosphatidic acid phosphohydrolase is pelletized when amniotic fluid is centrifuged at high speeds. The surface-active material is also pelletized under these conditions as was demonstrated by the presence of phosphatidylcholine and palmitate in the pellet. Lamellar bodies have been isolated which are free of microsomal and mitochondrial contamination from pig lung. These lamellar bodies show a significant amount of PAPase and cholinephosphotransferase activity. The concepts support our postulate that the lamellar bodies are an active site for surface-active material synthesis. The release of the surface-active material from the Type II cells have demonstrated that this occurs via the microtubular system. BIBLIOGRAPHIC REFERENCES: Delahunty, T.J. and Johnston, J.M.: "The Effect of Colchicine and Vinblastine on the Release of Pulmonary Surface-Active Material," J. Lipid Res. 17, 112-116, 1976. Jimenez, J.M. and Johnston, J.M.: "Fetal Lung Maturation IV: The Release of Phosphatidic Acid Phosphohydrolase and Phospholipids into Amniotic Fluid," Ped. Res. In press, July, 1976.